Japan says it has successfully completed its first test of a U.S.-developed missile interceptor, striking down a ballistic missile over the Pacific Ocean early Tuesday. As Naomi Martig reports from VOA's Asia News Center in Hong Kong, Washington and Japan have been working together for years to boost Japan's defense capabilities, especially against a threat by North Korea.

Japanese officials say the Standard Missile 3 interceptor knocked out a medium-range missile Tuesday in outer space, about 100 miles above the Pacific near the Hawaiian islands. Japan is the first country allowed by the United States to test the system, which is still being developed.

Television showed images of two objects colliding, followed by a huge explosion. U.S. and Japanese military personnel were then seen applauding the impact. Japan's Defense Minister, Shigeru Ishiba, says the test was extremely significant.

Ishiba says the credibility of Japan's interceptor capabilities has greatly improved. He says the country will be working hard to improve the system in order to further increase its credibility.

The SM3 system is designed to intercept short- to medium-range ballistic missiles. Japanese officials say the medium-range missile used in the test resembled those in North Korea's arsenal.

Japan has been working with the United States to develop a defense system against missiles that could originate in North Korea. Tokyo plans to put the SM-3 interceptors on four of its destroyers by 2011. The Japanese have felt a sense of urgency about their national defense ever since North Korea fired a test missile over their country in 1998.

Robert Ayson, director of studies at the Strategic and Defense Study Center in Australia, says Japan's security concerns go beyond North Korea, however.

"It's kind of an important restatement of the importance of seeing North Korea as a potential challenger," said Ayson. "But I think it goes further than that. I think also there's a message here about Japan's broader security concerns, and of course the China factor comes into this fairly easily as well."

Ayson says the successful test is likely to spark concern in Beijing. He says the Chinese are worried that the system could be used against Chinese missiles fired at Taiwan in the event of war across the Taiwan Strait.

"While Japan is justifying this again in terms of the North Korean threat, there is no guarantee that the system won't be used should a crisis in the strait erupt," he added.

Taiwan has been self-ruled since 1949, but Beijing still considers it part of the mainland. The Chinese have threatened to use military force to bring about reunification, and have almost 1,000 missiles aimed across the strait at Taiwan.